Introduction to Aerospace Engineering

Basic Principles of Flight

Ethirajan Rathakrishnan

• Publisher: Wiley
• Year: 2021
• ISBN:
  9781119806868
• Edition: 1
• Topic: Tecnología e ingeniería
• Subtopic: Ingeniería aeronáutica y astronáutica

Providesa broad and accessible introduction to the field of aerospace engineering, ideal for semester-long courses

Aerospaceengineering, the field of engineering focusedon the development of aircraft and spacecraft, is taught atuniversitiesin bothdedicated aerospace engineeringprograms as well as inwidermechanicalengineeringcurriculumsaround the world-yetaccessibleintroductory textbooks covering all essential areas of the subject are rare. Filling this significant gap in the market, Introduction to Aerospace Engineering: Basic Principles of Flight providesbeginningstudents with a strong foundational knowledge of thekeyconcepts they will further explore as they advance through their studies.

Designed to align with the curriculum of a single-semester course, this comprehensive textbook offers astudent-friendlypresentationthat combinesthe theoretical andpracticalaspectsofaerospaceengineering. Clear and concise chapters cover the laws of aerodynamics, pressure, and atmospheric modeling, aircraft configurations, the forces of flight, stability and control, rockets, propulsion, and more.Detailed illustrations, well-defined equations, end-of-chapter summaries, and ample review questionsthroughout the textensure students understand the core topics of aerodynamics, propulsion, flight mechanics, and aircraft performance.Drawnfromthe author'sthirty years'experience teaching the subject to countlessnumbers of universitystudents, this much-needed textbook:

• Explains basic vocabulary and fundamental aerodynamic concepts
• Describes aircraft configurations, low-speed aerofoils, high-lift devices, and rockets
• Covers essential topics including thrust, propulsion, performance, maneuvers, andstability and control
• Introduces each topicina concise and straightforward manneras students are guided through progressively more advanced material
• Includes access to companion website containing a solutions manual and lecture slides for instructors

Introduction to Aerospace Engineering: Basic Principles of Flight is the perfect "one stop" textbook forinstructors, undergraduates, and graduatestudents in Introduction to Aerospace Engineering or Introduction to Flight courses in Aerospace Engineering or Mechanical Engineering programs.

1
Basics

1.1 Introduction

Aerodynamics is the study of forces and the resulting motion of objects through the air. This word is coined with the two Greek words: aerios, concerning the air, and dynamis, meaning force. Judging from the story of Daedalus and Icarus,1 humans have been interested in aerodynamics and flying for thousands of years, although flying in a heavier‐than‐air machine has been possible only in the last century. Aerodynamics affects the motion of high‐speed flying machines, such as aircraft and rockets, and low‐speed machines, such as cars, trains, and so on. Therefore, aerodynamics may be described as a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a solid object. Aerodynamics is a subfield of fluid dynamics and gas dynamics. It is often used synonymously with gas dynamics, with the difference being that gas dynamics applies to all gases.

Understanding the flow field around an object is essential for calculating the forces and moments acting on the object. Typical properties calculated for a flow field include velocity, pressure, density, and temperature as a function of spatial position and time. Aerodynamics allows the definition and solution of equations for the conservation of mass, momentum, and energy in air. The use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer simulations forms the scientific basis for heavier‐than‐air flight and a number of other technologies.

Aerodynamic problems can be classified according to the flow environment. External aerodynamics is the study of flow around solid objects of various shapes. Evaluating the lift and drag on an airplane or the shock waves that form in front of the nose of a rocket are examples of external aerodynamics. Internal aerodynamics is the study of flow through passages in solid objects. For instance, internal aerodynamics encompasses the study of the airflow through a jet engine.

Aerodynamic problems can also be classified according to whether the flow speed is below, near or above the speed of sound. A problem is called subsonic if all the speeds in the problem are less than the speed of sound, transonic if speeds both below and above the speed of sound are present, supersonic if the flow speed is greater than the speed of sound, and hypersonic if the flow speed is more than five times the speed of sound.

The influence of viscosity in the flow dictates a third classification. Some problems may encounter only very small viscous effects on the solution; therefore the viscosity can be considered to be negligible. The approximations made in solving these problems is the viscous effect that can be regarded as negligible. These are called inviscid flows. Flows for which viscosity cannot be neglected are called viscous flows.

1.2 Overview

Humans have been harnessing aerodynamic forces for thousands of years with sailboats and windmills [1]. Images and stories of flight have appeared throughout recorded history [2], such as the legendary story of Icarus and Daedalus [3]. Although observations of some aerodynamic effects such as wind resistance (for example, drag) were recorded by Aristotle, Leonardo da Vinci, and Galileo Galilei, very little effort was made to develop a rigorous quantitative theory of airflow prior to the seventeenth century.

In 1505, Leonardo da Vinci wrote the Codex (an ancient manuscript text in book form) on the Flight of Birds, one of the earliest treatises on aerodynamics. He was the first to note that the centre of gravity of a flying bird does not coincide with its centre of pressure, and he describes the construction of an ornithopter with flapping wings similar to birds.

Sir Isaac Newton was the first to develop a theory of air resistance [4], making him one of the first aerodynamicists. As a part of that theory, Newton considered that drag was due to the dimensions of the body, the density of the fluid, and the velocity raised to the second power. These all turned out to be correct for low‐speed flow. Newton also developed a law for the drag force on a flat plate inclined towards the direction of the fluid flow. Using

for the drag force,

for the density,

for the area of the flat plate,

for the flow velocity, and

for the inclination angle, his law was expressed as

This equation is incorrect for the calculation of drag in most cases. Drag on a flat plate is closer to being linear with the angle of inclination as opposed to acting quadratically at low angles. The Newton formula can lead one to believe that flight is more difficult than it actually is, due to this overprediction of drag, and thus required thrust, which might have contributed to a delay in human flight. However, it is more correct for a very slender plate when the angle becomes large and flow separation occurs or if the flow speed is supersonic [5].

1.3 Modern Era

In 1738, the Dutch‐Swiss mathematician Daniel Bernoulli published Hydrodynamica. In this book Bernoulli described the fundamental relationship among pressure, density, and velocity, in particular Bernoulli's principle, which is one method to calculate aerodynamic lift [6]. More general equations of fluid flow – the Euler equations – were published by Leonhard Euler in 1757. The Euler equations were extended to incorporate the effects of viscosity in the first half of the eighteenth century, resulting in the Navier–Stokes equations.

Sir George ...